Conventionally, an X-ray CT apparatus is utilized for reconstructing and displaying an object image in a real time. Although single slice CT apparatus may use for reconstructing only one tomographic image, a multi slice CT apparatus may use for simultaneously reconstructing a plurality of tomographic images in a real time. One of the multi slice CT apparatus has been disclosed in U.S. Pat. No. 6,363,134. The multi slice CT apparatus is suitable for various diagnosis, including a needle insertion diagnosis. For the needle insertion diagnosis, when an operator inserts a needle to a patient, the multi slice CT apparatus reconstructs three tomographic images in a real time. For example, a first tomographic image is placed at a tip position of a needle, a second tomographic image is placed at a middle position of the needle, and a third tomographic image is placed at an end position of the needle in order to observe a whole imaging position of the inserted needle. During this needle insertion diagnosis, the operator stands besides a patient and operates the needle, with observing a displayed image near a gantry of the CT apparatus.
However, the conventional multi slice CT apparatus can provide only vertical omographic images. Consequently, it is difficult for an operator to appropriately understand an insertion state of the needle.